1. Field of the Invention
The present invention relates to an ink composition, an ink set and an inkjet recording method.
2. Description of the Related Art
Inkjet technology provides an image recording method for recording a color image. Inkjet technology has been applied to the fields of, for example, office printers or home printers, and has recently been applied to commercial printing.
A pigment is widely used as a coloring agent, which is one of the components contained in an ink material for inkjetting. The pigment is used dispersed in a medium such as water. When the pigment is dispersed for use, the particle diameter of the dispersed pigment, stability after dispersion, size uniformity, jettability from a jetting head, and the like are important. Techniques that improve such properties have been widely studied.
There are cases in which pigment-containing inks do not have satisfactory properties in terms of fixability (for example, abrasion resistance), water resistance, stain resistance, or the like, since such inks generally remain on the surface of a recording medium rather than penetrating into the recording medium.
In order to impart favorable water resistance and stain resistance to pigment-containing inks, an ink composition for inkjetting that contains self-dispersing polymer particles has been disclosed (see, for example, Japanese Patent No. 3069543).
In this regard, in the method of including the self-dispersing polymer particles, a polymer or resin contained in the ink composition works as a binder. Although it is recognized that fixability, water resistance or the like is improved, sufficient performance cannot be obtained in some cases since the fixability depends on the thermal properties of the polymer. In particular, when inkjet recording is performed at high speed, sufficient thermal fixation cannot be obtained in some cases.
In order to address these problems, a technique of using an ink in which a polymerizable monomer and a pigment are used in combination and curing the ink by a UV ray (UV inkjet) is widely known and used. The UV inkjet exhibits superior abrasion resistance, but the ink is generally a solvent-based ink and, therefore, is not preferred from an environmental point of view. In addition, when the inks contact each other prior to curing, the inks coalesce (spotting interference) and are unsuitable for high speed recording.
For an aqueous pigment ink, which is environmentally favorable, studies have been conducted for improving abrasion resistance by including a polymerizable monomer in an aqueous pigment ink and curing the same. For example, an inkjet recording method has been disclosed in which printing is performed on a recording medium by depositing (i) a reaction liquid containing a photopolymerization initiator and a reagent that forms an aggregate when contacted with an ink composition and (ii) an ink composition containing an acrylate monomer or a resin emulsion (see, for example, Japanese Patent No. 3642152). In addition, a one-component ink used for inkjet recording has been disclosed which contains a specific cationic oligomer and a photopolymerization initiator, together with a colorant and water (see, for example, Japanese Patent No. 3576862).